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Abstract:

An image compensation correction method and a banknote recognition and
detection device. The image compensation correction method is applied to
the banknote recognition and detection device. The banknote recognition
and detection device comprises: a micro controller; a programmable logic
device which is connected to the micro controller; an AD chip, a drive
circuit and a static random access memory which are connected to the
programmable logic device respectively; and a contact image sensor which
is connected to the AD chip and the drive circuit respectively. A
compensation correction lookup table is pre-stored in the static random
access memory, and the programmable logic device can acquire banknote
compensation correction data corresponding to a banknote image pixel
point by accessing the static random access memory, and send same to the
micro controller. Therefore, the micro controller acquires banknote
compensation correction data directly from the programmable logic device
rather than performing compensation correction on the obtained banknote
image pixel point any more, thereby improving the system performance of
the micro controller, and thus improving the work efficiency of the
banknote recognition and detection device.

Claims:

1. A method for compensating and correcting an image, applied to a device
for recognizing and verifying banknotes comprising a micro control unit,
a programmable logic device connected to the micro control unit, an
analog to digital (AD) chip, a drive circuit, and a static random access
memory each connected to the programmable logic device, and a contact
image sensor connected to the AD chip and the drive circuit respectively,
wherein the static random access memory pre-stores a lookup table for
compensation and correction; and the method comprises: receiving, by the
programmable logic device, a first configuration instruction output by
the micro control unit, and controlling, by the programmable logic
device, the drive circuit to drive the contact image sensor to collect
first banknote image pixels; converting, by the AD chip, the first
banknote image pixels into second banknote image pixels through analog to
digital conversion; and acquiring, by the programmable logic device, the
second banknote image pixels, using values of the second banknote image
pixels as address data, accessing the lookup table for compensation and
correction pre-stored in the static random access memory, finding
banknote compensation and correction data corresponding to the second
banknote image pixels, and transmitting the banknote compensation and
correction data to the micro control unit.

2. The method for compensating and correcting an image according to claim
1, wherein a process of creating the lookup table for compensation and
correction pre-stored in the static random access memory comprises:
receiving, by the programmable logic device, a second configuration
instruction output by the micro control unit, and controlling, by the
programmable logic device, the drive circuit to drive the contact image
sensor to collect first original image pixels; converting, by the AD
chip, the first original image pixels into second original image pixels
through analog to digital conversion; receiving, recording and storing,
by the programmable logic device, the second original image pixels, and
transmitting the second original image pixels to the micro control unit;
and receiving, by the micro control unit, the second original image
pixels, acquiring compensation and correction data corresponding to the
second original image pixels according to a compensation and correction
formula, creating the lookup table for compensation and correction with
the compensation and correction data, and storing the lookup table for
compensation and correction into the static random access memory.

3. The method for compensating and correcting an image according to claim
2, wherein the collecting, by the contact image sensor, first original
image pixels; and converting, by the AD chip, the first original image
pixels into second original image pixels through analog to digital
conversion, comprises: acquiring, by the contact image sensor,
black-level outputs of the first original image pixels by scanning black
calibration paper, and converting, by the AD chip, the black-level
outputs of the first original image pixels into black-level outputs of
the second original image pixels through analog to digital conversion;
and acquiring, by the contact image sensor, white-level outputs of the
first original image pixels by scanning white calibration paper, and
converting, by the AD chip, the white-level outputs of the first original
image pixels into white-level outputs of the second original image pixels
through analog to digital conversion.

4. The method for compensating and correcting an image according to claim
3, wherein the receiving and recording, by the programmable logic device,
the second original image pixels, comprises: receiving, by the
programmable logic device, the black-level outputs of the second original
image pixels, and recording the black-level outputs of the second
original image pixels as SB(i), i=0.about.N-1, where N is a total number
of the original pixels of the contact image sensor, and i is a serial
number of the original pixel; and receiving, by the programmable logic
device, the white-level outputs of the second original image pixels and
recording the white-level outputs of the second original image pixels as
SW(i), i=0.about.N-1, where N is a total number of the original pixels of
the contact image sensor, and i is a serial number of the original pixel.

5. The method for compensating and correcting an image according to claim
4, wherein the receiving, by the micro control unit, the second original
image pixels, acquiring compensation and correction data corresponding to
the second original image pixels according to a compensation and
correction formula, and creating the lookup table for compensation and
correction with the compensation and correction data, comprises:
receiving, by the micro control unit, the black-level outputs SB(i) of
the second original image pixels and the white-level outputs SW(i) of the
second original image pixels; acquiring, by the micro control unit, N
compensation and correction coefficients K(i) according to a coefficient
calculation formula K(i)=[SW(i)-SB(i)]/255; and acquiring, by the micro
control unit, all compensation and correction data corresponding to the
second original image pixels according to a compensation and correction
formula Y(i)=K(i)*[X(i)-SB(i)], and creating, by the micro control unit,
the lookup table for compensation and correction with the compensation
and correction data, wherein X(i) represents a value for the original
image, and Y(i) represents a corrected value.

6. The method for compensating and correcting an image according to claim
1, further comprising recognizing, by the micro control unit, the
banknote according to the banknote compensation and correction data, and
transmitting a banknote recognition result to an upper computer connected
to the micro control unit.

7. A device for recognizing and verifying banknotes, comprising: a micro
control unit, an AD chip, configured to perform analog to digital
conversion on received data; a drive circuit; a contact image sensor
which is connected to the AD chip and the drive circuit respectively, and
is configured to be driven by the drive circuit to collect pixels of an
image, and transmit the pixels of the image to the AD chip; a static
random access memory pre-storing a lookup table for compensation and
correction; and a programmable logic device which is connected to the
micro control unit, the AD chip, the drive circuit and the static random
access memory respectively, and is configured to receive a first
configuration instruction output by the micro control unit, control the
drive circuit to drive the contact image sensor to collect first banknote
image pixels, acquire second banknote image pixels obtained by the AD
chip through performing analog to digital conversion on the first
banknote image pixels, use values of the second banknote image pixels as
address data, access the lookup table for compensation and correction
pre-stored in the static random access memory, find banknote compensation
and correction data corresponding to the second banknote image pixels,
and transmit the banknote compensation and correction data to the micro
control unit.

8. The device for recognizing and verifying banknotes according to claim
7, wherein the AD chip is configured to convert first original image
pixels into second original image pixels through analog to digital
conversion; the programmable logic device is configured to receive a
second configuration instruction output by the micro control unit,
control the drive circuit to drive the contact image sensor to collect
the first original image pixels; and receive, record and store the second
original image pixels, and transmit the second original image pixels to
the micro control unit; and the micro control unit is configured to
receive the second original image pixels, acquire compensation and
correction data corresponding to the second original image pixels
according to a compensation and correction formula, create the lookup
table for compensation and correction with the compensation and
correction data, and store the lookup table for compensation and
correction into the static random access memory.

9. The device for recognizing and verifying banknotes according to claim
8, wherein the contact image sensor is configured to acquire black-level
outputs of the first original image pixels by scanning black calibration
paper; and acquire white-level outputs of the first original image pixels
by scanning white calibration paper.

10. The device for recognizing and verifying banknotes according to claim
9, wherein the AD chip is configured to convert the black-level outputs
of the first original image pixels into black-level outputs of the second
original image pixels through analog to digital conversion, and is
configured to convert the white-level outputs of the first original image
pixels into white-level outputs of the second original image pixels
through analog to digital conversion.

11. The device for recognizing and verifying banknotes according to claim
10, wherein the programmable logic device is configured to receive the
black-level outputs of the second original image pixels, and record the
black-level outputs of the second original image pixels as SB(i),
i=0.about.N-1, where N is a total number of the original pixels of the
contact image sensor, and i is a serial number of the original pixel; and
receive the white-level outputs of the second original image pixels and
record the white-level outputs of the second original image pixels as
SW(i), i=0.about.N-1, where N is a total number of the original pixels of
the contact image sensor, and i is a serial number of the original pixel.

12. The device for recognizing and verifying banknotes according to claim
11, wherein the micro control unit is configured to receive the
black-level outputs SB(i) of the second original image pixels and the
white-level outputs SW(i) of the second original image pixels; acquire N
compensation and correction coefficients K(i) according to a coefficient
calculation formula K(i)=[SW(i)-SB(i)]/255; and acquire compensation and
correction data corresponding to the second original image pixels
according to a compensation and correction formula Y(i)=K(i)*[X(i)-SB(i)]
to create the lookup table for compensation and correction, wherein X(i)
represents a value of the original image, and Y(i) represents a corrected
value.

13. The device for recognizing and verifying banknotes according to claim
7, further comprising: an upper computer which is connected to the micro
control unit and is configured to receive a banknote recognition result
output by the micro control unit.

Description:

[0001] The present application claims priority to Chinese Patent
Application No. 201310285100.9, entitled "IMAGE COMPENSATION CORRECTION
METHOD AND BANKNOTE RECOGNITION AND DETECTION DEVICE", filed on Jul. 8,
2013 with the State Intellectual Property Office of People's Republic of
China, which is incorporated herein by reference in its entirety.

FIELD

[0002] The disclosure relates to the technical field of banknote
recognition and banknote verification, particularly relates to a method
for compensating and correcting an image, and a device for recognizing
and verifying banknotes.

BACKGROUND

[0003] A contact image sensor (CIS) is a most common optical sensor used
in a device for recognizing and verifying banknotes. The CIS is normally
used to recognize a denomination of a banknote, front and back sides of
the banknote, and used to identify authenticity of the banknote. Multiple
sections are spliced inside a currently common CIS. Due to factors such
as fabrication and the splicing process, there are discrepancies among
light-sensitive units in various sections of the CIS, so various sections
of an original image directly collected by the CIS are different in
brightness, which affects the recognizing the banknote and identifying
authenticity of the banknote performed by the device for recognizing and
verifying banknotes. Thus the original image collected by the CIS needs
to be compensated and corrected.

[0004] In a conventional systematic solution, the compensation and
correction for the original image collected by the CIS is generally
performed by a micro control unit (MCU) in the device for recognizing and
verifying banknotes. Since the MCU also manages main tasks such as a
banknote recognition algorithm, and information communication as well, a
system performance of the MCN may be affected if the MCU spends too much
time on compensation and correction for the CIS, thus affecting operation
efficiency of the device for recognizing and verifying banknotes.

[0005] Therefore, a solution for improving the system performance of the
MCU while ensuring the MCU to compensate and correct the original image
collected by the CIS is highly required.

SUMMARY

[0006] In view of this, a method for compensating and correcting an image
and a device for recognizing and verifying banknotes are provided
according to embodiments of the disclosure, to improve a system
performance of a MCU while ensuring the MCN to compensate and correct an
original image collected by a CIS, so as to improve operation efficiency
of the device for recognizing and verifying banknotes.

[0007] A method for compensating and correcting an image, applied to a
device for recognizing and verifying banknotes including a micro control
unit, a programmable logic device connected to the micro control unit, an
analog to digital (AD) chip, a drive circuit, and a static random access
memory each connected to the programmable logic device, and a contact
image sensor connected to the AD chip and the drive circuit respectively,
where the static random access memory pre-stores a lookup table for
compensation and correction; the method includes:

[0008] receiving, by the programmable logic device, a first configuration
instruction output by the micro control unit, and controlling, by the
programmable logic device, the drive circuit to drive the contact image
sensor to collect first banknote image pixels;

[0009] converting, by the AD chip, the first banknote image pixels into
second banknote image pixels through analog to digital conversion; and

[0010] acquiring, by the programmable logic device, the second banknote
image pixels, using values of the second banknote image pixels as address
data, accessing the lookup table for compensation and correction
pre-stored in the static random access memory, finding banknote
compensation and correction data corresponding to the second banknote
image pixels, and transmitting the banknote compensation and correction
data to the micro control unit.

[0011] Optionally, a process of creating the lookup table for compensation
and correction pre-stored in the static random access memory includes:

[0012] receiving, by the programmable logic device, a second configuration
instruction output by the micro control unit, and controlling, by the
programmable logic device, the drive circuit to drive the contact image
sensor to collect first original image pixels;

[0013] converting, by the AD chip, the first original image pixels into
second original image pixels through analog to digital conversion;

[0014] receiving, recording and storing, by the programmable logic device,
the second original image pixels, and transmitting the second original
image pixels to the micro control unit; and

[0015] receiving, by the micro control unit, the second original image
pixels, acquiring compensation and correction data corresponding to the
second original image pixels according to a compensation and correction
formula, creating the lookup table for compensation and correction with
the compensation and correction data, and storing the lookup table for
compensation and correction into the static random access memory.

[0016] Optionally, the collecting, by the contact image sensor, first
original image pixels; and converting, by the AD chip, the first original
image pixels into second original image pixels through analog to digital
conversion, includes:

[0017] acquiring, by the contact image sensor, black-level outputs of the
first original image pixels by scanning black calibration paper, and
converting, by the AD chip, the black-level outputs of the first original
image pixels into black-level outputs of the second original image pixels
through analog to digital conversion; and

[0018] acquiring, by the contact image sensor, white-level outputs of the
first original image pixels by scanning white calibration paper, and
converting, by the AD chip, the white-level outputs of the first original
image pixels into white-level outputs of the second original image pixels
through analog to digital conversion.

[0019] Optionally, the receiving and recording, by the programmable logic
device, the second original image pixels, includes:

[0020] receiving, by the programmable logic device, the black-level
outputs of the second original image pixels, and recording the
black-level outputs of the second original image pixels as SB(i),
i=0˜N-1, where N is a total number of the original pixels of the
contact image sensor, and i is a serial number of the original pixel; and

[0021] receiving, by the programmable logic device, the white-level
outputs of the second original image pixels and recording the white-level
outputs of the second original image pixels as SW(i), i=0˜N-1,
where N is a total number of the original pixels of the contact image
sensor, and i is a serial number of the original pixel.

[0022] Optionally, the receiving, by the micro control unit, the second
original image pixels, acquiring compensation and correction data
corresponding to the second original image pixels according to a
compensation and correction formula, and creating the lookup table for
compensation and correction with the compensation and correction data,
includes:

[0023] receiving, by the micro control unit, the black-level outputs SB(i)
of the second original image pixels and the white-level outputs SW(i) of
the second original image pixels;

[0024] acquiring, by the micro control unit, N compensation and correction
coefficients K(i) according to a coefficient calculation formula
K(i)=[SW(i)-SB(i)]/255; and

[0025] acquiring, by the micro control unit, all compensation and
correction data corresponding to the second original image pixels
according to a compensation and correction formula
Y(i)=K(i)*[X(i)-SB(i)], and creating, by the micro control unit, the
lookup table for compensation and correction with the compensation and
correction data, where X(i) represents a value for the original image,
and Y(i) represents a corrected value.

[0026] Optionally the method for compensating and correcting an image
further includes:

[0027] recognizing, by the micro control unit, the banknote according to
the banknote compensation and correction data, and transmitting a
banknote recognition result to an upper computer connected to the micro
control unit.

[0028] A device for recognizing and verifying banknotes, includes:

[0029] a micro control unit,

[0030] an AD chip, configured to perform analog to digital conversion on
received data;

[0031] a drive circuit;

[0032] a contact image sensor which is connected to the AD chip and the
drive circuit respectively, and is configured to be driven by the drive
circuit to collect pixels of an image, and transmit the pixels of the
image to the AD chip;

[0033] a static random access memory pre-storing a lookup table for
compensation and correction; and

[0034] a programmable logic device which is connected to the micro control
unit, the AD chip, the drive circuit and the static random access memory
respectively, and is configured to receive a first configuration
instruction output by the micro control unit, control the drive circuit
to drive the contact image sensor to collect first banknote image pixels,
acquire second banknote image pixels obtained by the AD chip through
performing analog to digital conversion on the first banknote image
pixels, use values of the second banknote image pixels as address data,
access the lookup table for compensation and correction pre-stored in the
static random access memory, find banknote compensation and correction
data corresponding to the second banknote image pixels, and transmit the
banknote compensation and correction data to the micro control unit.

[0035] Optionally, the AD chip is configured to convert first original
image pixels into second original image pixels through analog to digital
conversion;

[0036] the programmable logic device is configured to receive a second
configuration instruction output by the micro control unit, control the
drive circuit to drive the contact image sensor to collect the first
original image pixels; and receive, record and store the second original
image pixels, and transmit the second original image pixels to the micro
control unit; and

[0037] the micro control unit is configured to receive the second original
image pixels, acquire compensation and correction data corresponding to
the second original image pixels according to a compensation and
correction formula, create the lookup table for compensation and
correction with the compensation and correction data, and store the
lookup table for compensation and correction into the static random
access memory.

[0038] Optionally, the contact image sensor is configured to acquire
black-level outputs of the first original image pixels by scanning black
calibration paper; and acquire white-level outputs of the first original
image pixels by scanning white calibration paper.

[0039] Optionally, the AD chip is configured to convert the black-level
outputs of the first original image pixels into black-level outputs of
the second original image pixels through analog to digital conversion,

[0040] and is configured to convert the white-level outputs of the first
original image pixels into white-level outputs of the second original
image pixels through analog to digital conversion.

[0041] Optionally, the programmable logic device is configured to receive
the black-level outputs of the second original image pixels, and record
the black-level outputs of the second original image pixels as SB(i),
i=0˜N-1, where N is a total number of the original pixels of the
contact image sensor, and i is a serial number of the original pixel; and
receive the white-level outputs of the second original image pixels and
record the white-level outputs of the second original image pixels as
SW(i), i=0˜N-1, where N is a total number of the original pixels of
the contact image sensor, and i is a serial number of the original pixel.

[0042] Optionally, the micro control unit is configured to receive the
black-level outputs SB(i) of the second original image pixels and the
white-level outputs SW(i) of the second original image pixels; acquire N
compensation and correction coefficients K(i) according to a coefficient
calculation formula K(i)=[SW(i)-SB(i)]/255; and acquire compensation and
correction data corresponding to the second original image pixels
according to a compensation and correction formula Y(i)=K(i)*[X(i)-SB(i)]
to create the lookup table for compensation and correction, where X(i)
represents a value of the original image, and Y(i) represents a corrected
value.

[0043] Optionally, the device for recognizing and verifying banknotes
further includes an upper computer which is connected to the micro
control unit and is configured to receive a banknote recognition result
output by the micro control unit.

[0044] According to the above technical solutions, a method for
compensating and correcting an image, and a device for recognizing and
verifying banknotes are provided. The method for compensating and
correcting an image is applied to a device for recognizing and verifying
banknote. The device for recognizing and verifying banknote includes a
micro control unit, a programmable logic device connected to the micro
control unit, an AD chip, a drive circuit, and a static random access
memory each connected to the programmable logic device, and a contact
image sensor connected to the AD chip and the drive circuit respectively.
In the provided device for recognizing and verifying banknote, the static
random access memory pre-stores a lookup table for compensation and
correction. The programmable logic device can obtain banknote
compensation and correction data corresponding to banknote image pixels,
and transmit the banknote compensation and correction data to the micro
control device. Thus, in the provided device for recognizing and
verifying banknote, the micro control device no longer compensates or
corrects banknote image pixels obtained. Instead, the micro control
device directly acquires banknote compensation and correction data from
the programmable logic device. The micro control device merely recognizes
the banknote according to the banknote compensation and correction data.
Thus, compensation and correction of the banknote is no longer performed
by the micro control device, thereby improving a system performance of
the micro control device, and improving operation efficiency of the
device for recognizing and verifying banknote.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] For clarity of the technical solutions in the embodiments of the
present disclosure or technical solutions in conventional technology,
drawings involved in the embodiments of the present disclosure or in the
conventional technology are briefly describes as follows. Apparently, the
drawings described below are a few embodiments, and persons of ordinary
skill in the art can derive other drawings according to the drawings
without any creative work.

[0046] FIG. 1 is a flow chart of a method for compensating and correcting
an image according to an embodiment of the disclosure;

[0047] FIG. 2 is a schematic structural diagram of a device for
recognizing and verifying banknotes according to an embodiment of the
disclosure;

[0048] FIG. 3 is a flow chart of a process of creating a lookup table for
compensation and correction pre-stored in a static random access memory
according to an embodiment of the disclosure; and

[0049] FIG. 4 is a flow chart of a method for compensating and correcting
an image according to an embodiment of the disclosure.

DETAILED DESCRIPTION

[0050] Technical solutions of the embodiments of the present disclosure
will be illustrated completely and clearly with the drawings for the
embodiments of the disclosure. Apparently, the described embodiments are
merely a few rather than all embodiments of the present disclosure. All
other embodiments obtained by persons of ordinary skill in the art based
on the embodiments of the present disclosure without creative work shall
fall within the protection scope of the present disclosure.

[0051] FIG. 1 is a flow chart of a method for compensating and correcting
an image. The method for compensating and correcting an image is applied
to a device for recognizing and verifying banknotes. FIG. 2 shows a
schematic structural diagram of a device for recognizing and verifying
banknotes. The device for recognizing and verifying banknotes includes: a
micro control unit 11, a programmable logic device 12 (Field-Programmable
Gate Array, FPGA) connected to the micro control unit 11, an analog to
digital (AD) chip 13, a drive circuit 14 and a static random access
memory (Static RAM, SRAM) 15, which are each connected to the
programmable logic device 12, a contact image sensor (CIS) 16 which is
connected to the AD chip 13 and the drive circuit 14 respectively, where
the static random access memory 15 pre-stores a lookup table for
compensation and correction. The method includes following steps S11 to
S13.

[0052] In step S11, the programmable logic device 12 receives a first
configuration instruction output by the micro control unit 11, and
controls the drive circuit 14 to drive the contact image sensor 16 to
collect first banknote image pixels.

[0053] When the device for recognizing and verifying banknotes verifies a
banknote, the micro control unit 11 outputs the first configuration
instruction to the programmable logic device 12, the programmable logic
device 12 receives the first configuration instruction, enters into a
mode for recognizing and verifying banknotes and then outputs a driving
signal to the drive circuit 14, to control the drive circuit 14 to drive
the contact image sensor 16 to collect first banknote image pixels.

[0054] In step S12, the AD chip 13 converts the first banknote image
pixels into second banknote image pixels through analog to digital
conversion.

[0055] The first banknote image pixels are analog voltage signals, and the
second banknote image pixels are digital signals.

[0056] In step S13, the programmable logic device 12 finds banknote
compensation and correction data corresponding to the second banknote
image pixels, and transmits the banknote compensation and correction data
to the micro control unit 11.

[0057] The programmable logic device 12 acquires the second banknote image
pixels, uses values of the second banknote image pixels as address data,
accesses the lookup table for compensation and correction pre-stored in
the static random access memory 15, finds the banknote compensation and
correction data corresponding to the second banknote image pixels, and
transmits the banknote compensation and correction data to the micro
control unit 11.

[0058] It can be understood that one banknote has multiple banknote image
pixels, and scanning the banknote by the contact image sensor 16 is for
collecting the banknote image pixels.

[0059] According to the above technical solutions, different from the
condition in conventional technology, compensation and correction of the
acquired banknote image pixels are no longer performed by the micro
control unit 11. Instead, the micro control unit 11 directly acquires the
banknote compensation and correction data from the programmable logic
device 12, and the micro control unit 11 merely recognizes the banknote
according to the banknote compensation and correction data. Therefore,
compensation and correction of the acquired banknote image pixels are no
longer performed by the micro control unit 1, thereby greatly reducing
the amount of data to be processed. With the method for compensating and
correcting an image according to the embodiment of the disclosure, not
only a system performance of the micro control unit 11 is improved, but
also a speed for processing the banknote image pixels is improved,
thereby improving operation efficiency of the device for recognizing and
verifying banknotes.

[0060] It is should be noted that the programmable logic device 12 may
transmit a single line of acquired banknote compensation and correction
data to the micro control unit 11. Alternatively, the programmable logic
device 12 may cache acquired banknote compensation and correction data,
and then transmit multiple lines of banknote compensation and correction
data to the micro control unit 11.

[0061] Continually receiving single lines of banknote compensation and
correction data makes the micro control unit 11 always in a data
processing state, which affects a system performance of the micro control
unit 11. To further optimize the system performance of the micro control
unit 11, the programmable logic device 12 may cache multiple lines of
banknote compensation and correction data, and then transmit the multiple
lines of banknote compensation and correction data together to the micro
control unit 11. The number of the lines of the banknote compensation and
correction data transmitted to the micro control unit 11 by the
programmable logic device 12 can be modified by modifying a program in
the programmable logic device 12. The number of the lines of the
transmitted banknote compensation and correction data may be determined
as desired, and is not limited according to the disclosure herein.

[0062] The programmable logic device 12 keeps transmitting the banknote
compensation and correction data to the micro control unit 11 while the
micro control unit 11 recognizes the banknote according to the acquired
banknote compensation and correction data, i.e., the acquirement of the
banknote compensation and correction data by the programmable logic
device 12 and the recognition of the banknote by the micro control unit
11 are performed simultaneously, and this processing manner is called as
"ping-pong cache". It is can be seen that the "ping-pong cache" improves
the operation efficiency of the device for recognizing and verifying
banknotes.

[0063] FIG. 3 is a flow chart of a process for creating a lookup table for
compensation and correction pre-stored in a static random access memory
according to an embodiment of the disclosure. The process includes
following steps S21 to S24.

[0064] In step S21, the programmable logic device 12 receives a second
configuration instruction output by the micro control unit 11, and
controls the drive circuit 14 to drive the contact image sensor 16 to
collect first original image pixels.

[0065] For creating a lookup table for compensation and correction, the
programmable logic device 12 receives a second configuration instruction
output by the micro control unit 11. Then the programmable logic device
12 enters an original image collecting mode, and outputs a drive signal
to control the drive circuit 14 to drive the contact image sensor 16 to
collect first original image pixels.

[0066] It can be understood for persons of skills in the art that through
scanning black calibration paper, the contact image sensor 16 can acquire
black-level outputs of the first original image pixels, i.e., black-level
outputs for each pixel of the contact image sensor 16; and through scan
white calibration paper, the contact image sensor 16 can acquire
white-level outputs of the first original image pixels, i.e., white-level
outputs of each pixel of the contact image sensor 16.

[0067] In step S22, the AD chip 13 converts the first original image
pixels into second original image pixels through analog to digital
conversion

[0068] The AD chip 13 converts the black-level outputs of the first
original image pixels into black-level outputs of second original image
pixels through analog to digital conversion.

[0069] The AD chip 13 converts the white-level outputs of the first
original image pixels into white-level outputs of second original image
pixels through analog to digital conversion.

[0070] In step S23, the programmable logic device 12 receives, records and
stores the second original image pixels, and transmits the second
original image pixels to the micro control unit 11.

[0071] The programmable logic device 12 receives the black-level outputs
of the second original image pixels, and records the black-level outputs
of the second original image pixels as SB(i), i=0˜N-1, (where N is
a total number of the original pixels of the contact image sensor, and i
is a serial number of the original pixel).

[0072] The programmable logic device 12receives the white-level outputs of
the second original image pixels and records the white-level outputs of
the second original image pixels as SW(i), i=0˜N-1, (where N is a
total number of the original pixels of the contact image sensor, and i is
a serial number of the original pixel).

[0073] In step S24, the micro control unit 11 receives the second original
image pixels, acquires compensation and correction data corresponding to
the second original image pixels according to a compensation and
correction formula, creates the lookup table for compensation and
correction with the compensation and correction data, and stores the
lookup table for compensation and correction into the static random
access memory 15.

[0074] The micro control unit 11 receives the black-level outputs of the
second original image pixels as SB(i), and the white-level outputs of the
second original image pixels as SW(i).

[0075] The micro control unit 11 acquires N compensation and correction
coefficients K(i) according to a coefficient calculation formula
K(i)=[SW(i)-SB(i)]/255.

[0076] The micro control unit 11 acquires all compensation and correction
data corresponding to the second original image pixels according to a
compensation and correction formula Y(i)=K(i)*[X(i)-SB(i)], (where X(i)
represents a value for the original image, and Y(i) represents a
corrected value), creates the lookup table for compensation and
correction with the compensation and correction data, and stores the
lookup table for compensation and correction in the static random access
memory 15.

[0077] It should be noted that the micro control unit 11 is not directly
connected to the static random access memory 15, and needs to store the
formed lookup table for compensation and correction into the static
random access memory 15 through the programmable logic device 12.
Therefore, affection on a system performance of the micro control unit
11, caused by frequent data exchange between the micro control unit 11
and the static random access memory 15 resulted from direct connection of
the micro control unit 11 and the static random access memory 15, is
effectively avoided.

[0078] The process that the micro control unit 11 acquires all
compensation and correction data corresponding to the second original
image pixels according to a compensation and correction formula
Y(i)=K(i)×[X(i)-SB(i)] (X(i) represents a value for the original
image, and Y(i) represents a corrected value), and creates the lookup
table for compensation and correction, is as follows.

[0079] X(i) is in a range of 0-255, and in a case that i is a fixed value,
corresponding values of Y(i) may be acquired through traversing 256 input
values. For example, in a case that i is equal to 0, K(0) and SB(0) can
be calculated according to step S23 and step S24, values of X(0) are
input when i traverses from 0 to 255, then 256 corresponding values of
Y(0) may be acquired, which are all compensation and correction data with
respect to the first pixel X(0). Similarly, by increasing i by one every
time, compensation and correction data corresponding to all pixels of the
contact image sensor 16 can be acquired, so that an complete lookup table
for compensation and correction with respect to the contact image sensor
16 is obtained.

[0080] For example, all possible compensation and correction values y(n,
x) can be pre-calculated according to the compensation and correction
formula Y(i)=K(i)×[X(i)-SB(i)], where n represent a nth pixel (n is
different from i, n represents an nth pixel, and i is a number of an
original pixel, which starts from 0, i.e., n=i+1), x (equivalent to the
foregoing X(i) represents a value for the original image. The lookup
table may be completed in an ascending order of n and x, and the possible
compensation and correction values may be serialized and stored in the
static random access memory 15 in an order of the lookup table.

[0081] The lookup table for compensation and correction with respect to N
pixels may be as follows.

[0082] After the programmable logic device 12 receives the first
configuration instruction and enters into the mode for recognizing and
verifying banknotes, it is assuming that the base address of the static
random access memory 15 is Base0, and a current output value of a tenth
pixel of the contact image sensor 16 is 50, then an address of the static
random access memory 15 which is accessed by the programmable logic
device 12 is (Base0+256×9+50), i.e., content of y(10, 50) is a
compensated and corrected value for the tenth pixel. Similarly,
compensations and corrections for all pixels can be accomplished.

[0083] Since all possible 256 gray input values of x are traversed, the
table is complete, and can represent all possible output results. Thus in
a case that a system of the device for recognizing and verifying
banknotes operates in the recognition mode, the image is compensated and
corrected by a non-time-consuming way in which the programmable logic
device accesses and reads the static random access memory 15, instead of
time-consuming conventional multiplication calculation of the micro
control unit 11. Taking IS61WV20488BLL as an example, one read operation
can be finished in 10 ns, which occupies little system time. Meanwhile,
with the device for recognizing and verifying banknotes according to the
disclosure, a conventional way, in which the micro control unit 11
performs serial compensation after the scan, is broken through. After the
scanning of the banknote, the compensated image can be synchronously
output, which occupies little time of the micro control unit 11, thus the
micro control unit 11 can concentrate on the banknote recognition
algorithm and communication of the recognition result. With ping-pang
cache, preprocessing for the correction of the image and the banknote
recognition algorithm can be performed in parallel, real-time and
high-speed processing ability is outstanding, and the system performance
of the micro control unit 11 is greatly improved, thereby improving
operation efficiency of the device for recognizing and verifying
banknotes.

[0084] Based on FIG. 1, FIG. 4 is a flow chart of a method for
compensating and correcting an image according to an embodiment of the
disclosure, and the method may further include following steps S14 to
S15.

[0085] In step S14, the micro control unit 11 recognizes the banknote
according to the banknote compensation and correction data, and transmits
a banknote recognition result to an upper computer connected to the micro
control unit 11.

[0086] In step S15, the micro control unit 11 outputs the first
configuration instruction to the programmable logic device 12 again, to
instruct the programmable logic device 12 to acquire compensation and
correction data for next banknote.

[0087] Corresponding to above method embodiments, a device for recognizing
and verifying banknotes is provided according to an embodiment of the
disclosure, as shown in FIG. 2. The device for recognizing and verifying
banknotes includes:

[0089] Optionally, the micro control unit 11 is a digital signal processor
(DSP).

[0090] The AD chip 13 is configured to perform analog to digital
conversion on received data. The AD chip 13 according to an embodiment of
the disclosure may be AD9822.

[0091] The static random access memory 15 pre-stores a lookup table for
compensation and correction. A process of creating the lookup table for
compensation and correction is as shown in FIG. 3, and is not described
herein.

[0092] The contact image sensor 16 is connected to the AD chip 13 and the
drive circuit 14 respectively, and is configured to be driven by the
drive circuit 14 to collect pixels of an image, and transmit the pixels
of the image to the AD chip 13.

[0093] The contact image sensor 16 is used in a scanner, and is a
component where light-sensing units are densely arranged, and
light-sensing units directly collect information of light reflected by an
object being scanned. According to an embodiment of the disclosure, the
contact image sensor 16 is mainly configured to scan a banknote, to
collect pixels of the image of the banknote.

[0094] The drive circuit 14 provides a LED constant current driver, a
line-scanning synchronization signal, and a clock signal for
synchronously outputting pixel-points, etc. controlled by the contact
image sensor 16, the drive circuit 14 drives the contact image sensor 16
to perform photoelectric conversion on a scanned light signal, and output
a measurable analog signal.

[0095] The programmable logic device 12 is connected to the micro control
unit 11, the AD chip 13, the drive circuit 14 and the static random
access memory 15 respectively, and is configured to receive a first
configuration instruction output by the micro control unit 11, control
the drive circuit 14 to drive the contact image sensor 16 to collect
first banknote image pixels, acquire second banknote image pixels
obtained by the AD chip 13 through performing analog to digital
conversion on the first banknote image pixels, use values of the second
banknote image pixels as address data, access a lookup table for
compensation and correction pre-stored in the static random access memory
15, find banknote compensation and correction data corresponding to the
second banknote image pixels, and transmit the banknote compensation and
correction data to the micro control unit 11.

[0096] It is should be noted that the first banknote image pixels
collected by the contact image sensor 16 are analog voltage signals, the
second banknote image pixels obtained by the AD chip 13 performing analog
to digital conversion on the first banknote image pixels are digital
signals. The AD chip 13 according to an embodiment of the disclosure is
mainly configured for analog to digital conversion.

[0098] In the programmable logic device 12 are provided with functional
modules such as a clock management module, a CIS driving control module,
an AD configuration module, a SRAM control module and an image caching
module, and the programmable logic device 12 achieves cooperation among
the function modules through internal programming.

[0099] The clock management module provides clock signals for function
modules in the programmable logic device 12, the CIS driving control
module is capable of outputting signals such as a resolution setting
signal, a LED constant current driver, a line-scanning synchronization
signal and a clock signal for synchronously outputting pixel-points, to
the drive circuit 14. The AD configuration module is for configuring an
analog to digital conversion device and implements configurations of
internal registers such as a multi-channel operation mode, a programmable
gain controller, a programmable offset device, and a reference voltage,
for the AD chip 13. The SRAM control module performs reading and writing
accesses to the static random access memory 15, and implements looking up
the lookup table for compensation and correction data and a real-time
compensation and correction function oft an original image for the
contact image sensor 16. The image caching module splices image data
output by the AD chip 13, caches multiple lines of data and transmit the
multiple lines of data to the micro control unit 11 to form the an image
of the banknote.

[0100] The principles for the device for recognizing and verifying
banknotes as shown in FIG. 2 and components thereof are the same as those
described in the foregoing method embodiments, and are not repeated
herein.

[0101] The device for recognizing and verifying banknotes based on FIG. 2
may further includes:

[0102] an upper computer connected to the micro control unit 11 and
configured to receive a banknote recognition result output by the micro
control unit 11.

[0104] In summary, in a case that the device for recognizing and verifying
banknotes according to the embodiment of the disclosure verifies the
banknote, the conventional compensation and correction of banknote image
pixels by a micro control unit, is substituted with a process that the
banknote compensation and correction data are obtained by the
programmable logic device through accessing the static random access
memory 15. After the scanning of the banknote, the banknote compensation
and correction data are synchronously output to the micro control unit
11, and the micro control unit 11 receives the banknote compensation and
correction data and recognizes the banknote. Compared with conventional
technology, an amount of data to be processed by the micro control unit
11 is greatly reduced. Thus, with the device for recognizing and
verifying banknotes provided according to the embodiment of the
disclosure, not only a system performance of the micro control unit 11 is
improved, but also a speed for processing the banknote image pixels is
improved, thereby improving operation efficiency of the device for
recognizing and verifying banknotes.

[0105] The embodiments of the present disclosure are described in a
progressive manner and each embodiment places emphasis on the difference
from other embodiments. Therefore, one embodiment can refer to other
embodiments for the same or similar parts.

[0106] According to the description of the disclosed embodiments, the
disclosure can be implemented or used by a person of skills in the art.
Various modifications made to these embodiments may be obvious for
persons of skills in the art, and a normal principle defined in the
disclosure may be implemented in other embodiments without departing from
the spirit or scope of the disclosure. Therefore the disclosure is not
limited to the embodiments described herein but confirms to a widest
scope in accordance with principles and novel features disclosed in the
disclosure.